Applications exist wherein it is necessary to provide clamping means for clamping one end of a resilient gasket into an opening. For example, considering U.S. Pat. No. 4,387,900 assigned to the Assignee of the present invention, there is disclosed therein a gasket intended for use in an opening in manhole bases and the like wherein the gasket disclosed therein is intended for in situ installation within the openings of manhole bases which have either been precast at the factory or cored either at the factory or at a job site. The gasket is provided with an outer flange which is urged in an outward radial direction by a clamping band, which, in the clamped position, places the gasket under compression to effect a fluid-tight seal between the gasket and the opening in the manhole base. The inner end of the gasket forms a watertight seal with a pipe extended therethrough.
The clamping band described in U.S. Pat. No. 4,387,900 is a plastic band which is presized preparatory to delivery at the job site and is provided with a small insert portion hingedly connected to one of the free ends of the clamping band. The clamping band is expanded by suitable hydraulic expansion apparatus, the wedge is moved into the gap between the two free ends of the clamping band and the expansion force exerted on the clamping band is released to maintain the clamping band in the locked position.
Clamping bands of the above design suffer from a number of disadvantages which include the difficulty in insertion of the insert member and the inability of the clamping band to compensate for deviations in the nominal diameter of the opening formed in the manhole base. The latter problem is quite prevalent when dealing with manhole bases in which the openings have been cored due to the fact that the coring members, after undergoing wearing, tend to core openings which are smaller in diameter by a significant amount compared with the openings which are cored with new coring equipment.
An improvement in the clamping band has been introduced by virtue of pending application Ser. No. 778,690 filed Sept. 23, 1985 and assigned to the Assignee of the present invention. In the clamping band described in the aforementioned copending application, the hingedly mounted insert has been eliminated and the free ends of the clamping band butt together when the band has been suitably expanded and the expansion forces have then been released after the free ends have snapped outwardly and into engagement with one another. Although this design eliminates the problems introduced by the hindgedly mounted insert, the critical sizing problem remains unresolved.
In addition to the above mentioned problems, it is also desirable to provide a clamping band which, although providing excellent clamping and compressive forces when properly mounted, is nevertheless easily removable and reusable.